Egg rejection by Iberian azure-winged magpies Cyanopica cyanus in the absence of brood parasitism

The Iberian azure-winged magpie Cyanopica cyanus shows a remarkable ability to discriminate against great spotted cuckoo Clamator glandarius eggs. Here, I studied whether egg recognition in this species could be a derived feature resulting from intra-specific brood parasitism. Azure-winged magpies showed a very high level of discrimination and rejection of great spotted cuckoo models (73.7%), and of conspecific eggs (42.8%), even when no evidence of great spotted cuckoo or conspecific brood parasitism has been found in the population. Azure-winged magpie discriminated more readily than magpies, the current favourite host of the great spotted cuckoo. The high rejection rate of conspecific eggs by the azure-winged magpie suggests that it is quite possible that egg discrimination in this species evolved in response to conspecific brood parasitism rather than to cuckoo parasitism.     

Synchronic east–west divergence in azure‐winged magpies (Cyanopica cyanus) and magpies (Pica pica)*

Morphometric and genetic analyses were performed to investigate the relationships between populations of the azure‐winged magpie (Cyanopica cyanus). In the morphometric analysis 193 specimens were included representing seven of the nine currently accepted subspecies. Among eight characters analysed, four showed significant differences between samples from Spain and Asia. In contrast, the Asian populations/subspecies are not differentiated morphologically except Cyanopica cyanus japonica. The genetic analysis was based on two mitochondrial sequences (control region, cytochromeb gene). The results are in accordance with the morphometric analysis, showing a clear distinction between birds from the western and eastern distribution ranges. The differentiation of C. c. japonica is not found at the sequence level. Both genetic and morphological data support species status of C. cyanus and Cyanopica cooki. The magpie (Pica pica) was included in the phylogenetic study for comparing intraspecific variation. As in C. cyanus, two clearly separated groups are found, one of them containing the far‐eastern populations (Pica pica jankowskii and Pica pica sericea) and the other the remaining subspecies studied. For both the azure‐winged magpie and the magpie the sequence data imply an east–west differentiation, probably caused by long lasting isolation that may have even started in the Pliocene or repeated expansions/restrictions of distribution ranges during the Pleistocene.     

Age-related differences in plumage characteristics of male tree swallows Tachycineta bicolor: hue and brightness signal different aspects of individual quality

Age-related differences in plumage characteristics of birds can be the result of differential survival of more ornamented individuals, within-individual changes in plumage attributes with age, or a combination of both. In this study, we investigated age-class related differences in plumage attributes of male tree swallows Tachycineta bicolor by performing both cross-sectional and longitudinal analyses. Male tree swallows in their first breeding season do not display delayed plumage maturation, and possess, like experienced breeders, metallic green to metallic blue iridescent plumage on their dorsal surface. Our results showed that, at the population level, older males were brighter and reflected light maximally at shorter wavelengths (i.e. were more blue). Differences in plumage brightness were most likely caused by changes within individuals as males increased in brightness between the first time they were captured and the subsequent year. Differences in hue, however, were not due to within-individual changes, but rather appear to be the result of greener individuals having lower survival and/or nest site fidelity. Indeed, relatively dull, greener birds had a lower probability of being recaptured the subsequent year. In contrast, we found that if birds captured in their first year as breeding adults were relatively bright, hue was not related to the probability of recapture. These results suggest that plumage attributes in male tree swallows have the potential of being honest signals of quality. Furthermore, plumage brightness and plumage hue might signal different aspects of male quality in this species.     

Blood parasites, leucocytes and plumage brightness in the Cirl Bunting, Emberiza cirlus

1. Although a female preference for pairing with brightly plumaged males has been reported in many species, the reasons for this choice are not fully understood.
2. Parasites have been proposed as playing an important role in shaping these preferences because, by pairing with brightly coloured individuals, females can obtain parasite-free and/or more healthy mates.
3. In this paper one of the predictions of this hypothesis is tested, namely a higher health level in brightly coloured individuals, by analysing the relationships among blood parasites, leucocyte levels and plumage brightness in the Cirl Bunting, Emberiza cirlus .
4. Two species of blood parasites were detected. Whereas a lower body condition was detected in individuals infected by Leucocytozoon cambournaci, no such differences were associated with Plasmodium relictum infections. Infected individuals showed higher total leucocyte counts than non-infected individuals.
5. Colour intensity of carotenoid derived colorations was negatively correlated to the relative proportion of lymphocytes and positively correlated to the relative presence of heterophils. Furthermore, the size of yellow feathered areas was positively correlated with the absolute number of leucocytes and the relative presence of heterophils. Only some of these relationships were found for non-carotenoid derived traits.
6. These results suggest that male plumage yellow coloration in the Cirl Bunting is a reliable indicator of health status and supports the hypothesis that females obtain more parasite-free mates if they pair with brightly coloured individuals.     

Within-male melanin-based plumage and bill elaboration in male house sparrows

If there is a cost to producing a dark color patch, the size of a patch may not correspond with its pigment concentration. The plumage of male house sparrows represents a case of dark, melanin-based ornamentation, but also a case of neglecting the composite nature of dark signals in birds. Here, I investigated what kind of associations exist between the brightness, chroma, and hue of dark integumentary patches and the size of a secondary sexual trait, the bib, in male house sparrows. I found that males with a larger bib also had a darker bib and bill, and a more saturated bib, bill, epaulets, head crown, and breast than small-bibbed males. Male bib coloration in terms of brightness and chroma was more strongly related to bib size than the coloration of other integumentary patches. However, with respect to hue, only the hue of the bill and cheeks was related to bib size. My results indicate that size, brightness, and chroma of the bib, but also chroma of other deeply colored patches, convey redundant information about the signaler's quality in male house sparrows.     

Genome‐wide variation in DNA methylation is associated with stress resilience and plumage brightness in a wild bird

Individuals often differ in their ability to cope with challenging environmental and social conditions. Evidence from model systems suggests that patterns of DNA methylation are associated with variation in coping ability. These associations could arise directly if methylation plays a role in controlling the physiological response to stressors by, among other things, regulating the release of glucocorticoids in response to challenges. Alternatively, the association could arise indirectly if methylation and resilience have a common cause, such as early‐life conditions. In either case, methylation might act as a biomarker for coping ability. At present, however, relatively little is known about whether variation in methylation is associated with organismal performance and resilience under natural conditions. We studied genome‐wide patterns of DNA methylation in free‐living female tree swallows (Tachycineta bicolor) using methylated DNA immunoprecipitation (MeDIP) and a tree swallow genome that was assembled for this study. We identified areas of the genome that were differentially methylated with respect to social signal expression (breast brightness) and physiological traits (ability to terminate the glucocorticoid stress response through negative feedback). We also asked whether methylation predicted resilience to a subsequent experimentally imposed challenge. Individuals with brighter breast plumage and higher stress resilience had lower methylation at differentially methylated regions across the genome. Thus, widespread differences in methylation predicted both social signal expression and the response to future challenges under natural conditions. These results have implications for predicting individual differences in resilience, and for understanding the mechanistic basis of resilience and its environmental and social mediators.     

Winter male plumage coloration correlates with breeding status in a cooperative breeding species

The function of colored ornaments is usually related to thesignaling of individual quality in intra- and intersexual interactions.In cooperative breeding species, where only a fraction of themale population access the breeding status and the other fractionhas the option to help breeding pairs, colored traits mightprovide the females with a reliable information on the qualityof potential mate. Males of the cooperative breeding azure-wingedmagpies (Cyanopica cyanus) display conspicuous blue plumagecoloration. Here we explored the role played by structural bluecoloration of males and the probability of becoming a breederor a helper. Birds were trapped during 4 consecutive years,and feather coloration was measured with a spectrometer. Malesthat became breeders had a more brilliant and saturated bluecoloration and showed a more violet hue in the nonbreeding periodcompared with birds that became helpers. Breeding males alsoshowed a seasonal decline in blueness, whereas the color propertiesof helpers were constant throughout the year. Blueness of individualstrapped in the nonbreeding period was positively correlatedwith body size and condition. These findings are consistentwith a scenario in which nonbreeding blue plumage colorationmay function as a signal of individual quality in the azure-wingedmagpie at the pair formation time and add to growing evidencesuggesting that the nonbreeding season appears particularlyimportant in impacting breeding roles in cooperative breedingbirds.     

Carotenoid-based sexual coloration and body condition in nesting male sticklebacks

The extent, corrected for body size, and intensity of nuptial coloration of breeding male three-spined sticklebacks Gasterosteus aculeatus L. from a Scottish freshwater population were highly variable but correlated, both in the field and after a period of nest-building in the laboratory. However, marked changes in coloration occurred between the field and the laboratory screenings and the coefficients of variation amongst males decreased. In general, intensity of coloration increased between the field and laboratory screenings, but changes in size-corrected extent were not consistently directional. For both indices, there was a negative relationship between the field value and amount by which colour changed between sampling sessions, with fish that were initially the dullest gaining most in colour. Size-corrected extent and (in particular) intensity of coloration in the field sample were associated positively with body condition measured post mortem and there was a negative, though non-significant, relationship between the extent of coloration and the proportion of white cells in the blood. No such associations were found for the laboratory colour screening. The concentration of astaxanthin in the lower jaw was related strongly and positively to both size-corrected extent and intensity of coloration at the laboratory screening and related negatively, though non-significantly, to proportional white cell counts. These data have implications both for the interpretation of previous laboratory studies and for the design of future experiments, and suggest that coloration is only a true indicator of male quality when measured in the field.     

Female plumage colour influences seasonal oxidative damage and testosterone profiles in a songbird

Across diverse taxa, morphological traits mediate social interactions and mate selection. Physiological constraints on signal elaboration have been widely documented, but the potential for trait display to influence physiological state remains poorly understood. We tested for the presence of causal links between ventral plumage colour—a trait known to covary with reproductive performance—and physiological measures in female North American barn swallows, Hirundo rustica erythrogaster. Naturally darker swallows have lower levels of plasma oxidative damage. Females manipulated to display darker ventral plumage during reproduction rapidly decreased oxidative damage, adopting the physiological state of naturally darker individuals. These results support the presence of a social mechanism that links static plumage traits with the physiological state of their bearer during trait advertisement, long after the completion of signal development.     

Testosterone, plumage colouration and extra-pair paternity in male North-American barn swallows

In most monogamous bird species, circulating testosterone concentration in males is elevated around the social female's fertile period. Variation in elevated testosterone concentrations among males may have a considerable impact on fitness. For example, testosterone implants enhance behaviours important for social and extra-pair mate choice. However, little is known about the relationship between natural male testosterone concentration and sexual selection. To investigate this relationship we measured testosterone concentration and sexual signals (ventral plumage colour and tail length), and determined within and extra-pair fertilization success in male North American barn swallows (Hirundo rustica erythrogaster). Dark rusty coloured males had higher testosterone concentrations than drab males. Extra-pair paternity was common (42% and 31% of young in 2009 and 2010, respectively), but neither within- nor extra-pair fertilization success was related to male testosterone concentration. Dark rusty males were less often cuckolded, but did not have higher extra-pair or total fertilization success than drab males. Tail length did not affect within- or extra-pair fertilization success. Our findings suggest that, in North American barn swallows, male testosterone concentration does not play a significant direct role in female mate choice and sexual selection. Possibly plumage colour co-varies with a male behavioural trait, such as aggressiveness, that reduces the chance of cuckoldry. This could also explain why dark males have higher testosterone concentrations than drab males.     

Correlated changes in male plumage coloration and female mate choice in cardueline finches

The coevolution of extravagant male traits and female mate preferences is a central tenet of sexual selection theory. In lineages in which males have developed more elaborate sexual characters, females favour the most extreme expression of the trait. In some taxa, however, ornamental displays have evolved from more to less exaggerated states. Under these circumstances, it is unclear whether females show preferences for an ancestral male condition or for the current, less elaborate display. Here, we tested female mate preferences relative to male ornamental coloration in two species of cardueline finch (the American goldfinch, Carduelis tristis, and pine siskin, Carduelis pinus) that have evolved less elaborate carotenoid-based colour displays from more elaborately coloured ancestral states. We presented females of each species with a choice of males having either large patches of red colour (the elaborate, ancestral condition) or with species-typical patches of yellow colour (the less elaborate, derived state). Female goldfinches and siskins showed consistent preferences for the natural colour displays of males, and not for the more elaborate, ancestral colour pattern. Previous research on another cardueline finch taxon (a subspecies of the house finch, Carpodacus mexicanus griscomi), however, showed that females prefer more elaborate, ancestral coloration to the current form of reduced colour expression. The lack of congruence between male trait expression and female trait preference in the lineage with the most recently derived reduction in trait expression suggests that there may be evolutionary lags in the correspondence between male traits and female preferences. A shift in the expression of male coloration appears to be the first step towards the evolution of reduced colour displays in these finches.     

Female preferences for male golden snub-nosed monkeys vary with male age and social context

Age is a key factor affecting sexual selection, as many physical and social traits are age-related. Although studies of primate mate choice often consider particular age-related traits, few consider the collective effects of male age. We tested the hypothesis that female golden snub-nosed monkeys Rhinopithecus roxellana prefer prime aged males (10–15 years) over younger and older males. We examined a habituated, provisioned troop during a 3-year study in the Qinling Mountains, China. Prime age males were more likely to be resident males of 1-male units (OMUs) than males of other ages. Since females are free to transfer between OMUs, the number of females per OMU can be indicative of female preferences. We examined the number of females per OMU, and found that it increased with resident male age up to 7–8 years, and declined after 12 years, such that prime age resident males had more females than other resident males. Females also initiated extra-unit copulations with high-ranking prime age males at significantly higher rates than with other males. Nevertheless, females tended to transfer from OMUs with high-ranking, older resident males to those with low-ranking, younger resident males. Thus, females appear to use different strategies when choosing social mates and extra-unit mates (i.e., different social contexts). We speculate that females may perceive early signs of aging in males and trade off the benefits and costs of high rank versus male senescence. This study lays the groundwork for future studies that examine possible direct and indirect benefits of such strategies.     

Female choice and male competition in longear sunfish

Mating systems with spatial clumping of nests or display sitestheoretically can result from female preference for clumpedmales or from competitive interactions among males. We testedpredictions derived from these two types of models against observationsof nest dispersion, mating success, and alternative male matingtactics in a naturally occurring population of central longearsunfish (Lepomis megalotis megalotis). The data were consistentwith models for male-initiated spatial clumping of nest sites;no evidence of female preference for clumped nests was found.We observed that large males had greater mating success thansmall males and that solitarily nesting males were larger thancolonial males; the most successful males were solitary nesters.Mating success of large males did not increase with colony size.Furthermore, colonial males were often cuckolded by neighbors,whereas solitary males were not cuckolded. We propose that colonialnesting is maintained in longear sunfish because group nestingallows subordinate males to obtain access to females.     

Individual quality and carotenoid‐based plumage ornaments in male red bishops (Euplectes orix): plumage is not all that counts

Males in many bird species develop elaborate carotenoid‐based plumage ornaments that play an important role as signals of individual quality in intra‐ or intersexual selection. In the present study, we investigated which of several factors related to male condition and health affect the brightness and coloration of the carotenoid‐based orange–red breeding plumage in males of the red bishop (Euplectes orix), a polygynous and sexually dimorphic weaverbird species. The study revealed a very complex pattern, with the relationships between plumage traits and both heterophil‐to‐lymphocyte ratio and blood parasite load varying considerably among seasons, suggesting a strong influence of environmental conditions. Furthermore, overall condition of males strongly affected the association pattern between plumage traits and other factors, with males in bad condition being forced to allocate resources away from plumage elaboration to body maintenance or the enhancement of immune functions, whereas males in good condition can afford to invest in plumage ornamentation without obvious detrimental effects on health. Thus, females cannot rely on plumage characteristics alone to gather information on male quality, but have to assess additional traits that advertise general male health status. Perhaps surprisingly, testosterone levels were not related to male plumage characteristics. © 2010 The Linnean Society of London, Biological Journal of the Linnean Society, 2010, 99 , 384–397.     

Parental care does not vary with age‐dependent plumage in male Saffron Finches Sicalis flaveola

The status signalling hypothesis states that conspicuous male plumage varies among males and serves as an honest signal of male quality and competitive ability. We expected immature‐plumaged males of the Saffron Finch Sicalis flaveola to feed their incubating mates and nestlings and remove faecal sacs at lower rates than those of mature‐plumaged males. We also predicted that females paired with immature‐plumaged males would compensate for their mates’ lower contribution. We found no differences in either feeding rates or sanitation rates between immature‐ and mature‐plumaged males. Similarly, females mated to immature‐ and mature‐plumaged males fed nestlings at equivalent rates. Apparently, male plumage colour and age are not reliable signals of the ability of a male Saffron Finch to provide for his mate and offspring.     

Neurons discovered in male Helicoverpa zea antennae that correlate with pheromone-mediated attraction and interspecific antagonism

Responses of single receptor neurons in the antennae of male Helicoverpa zea to sex pheromone components and to behavioral antagonists were recorded using a cut-sensillum extracellular recording technique. Three types of sensilla were identified from sampling 325 male-specific sensilla trichodea located at the lateral edge of antennomeres. The majority of these sensilla (71%) contained a receptor neuron tuned to the principal sex pheromone component (Z)-11-hexadecenal. A second sensillar type (10%) contained a receptor neuron that responded only to (Z)-9-tetradecenal. A third sensillar type (19%) contained a large-spiking neuron tuned to the secondary pheromone component (Z)-9-hexadecenal, but this neuron also could be stimulated to equivalent spike frequencies by the same emitted amounts of (Z)-9-tetradecenal. A smaller-spiking neuron in this sensillar type responded to two compounds known to act only as behavioral antagonists, (Z)-11-hexadecen-1-ol and (Z)-11-hexadecenyl acetate, and to (Z)-9-tetradecenal. Cross-adaptation studies confirmed the presence of one large- and one small-spiking neuron in the third sensillar type. Dose-response studies correlated to collected stimuli amounts showed that the large-spiking neuron in the third sensillar type was equally tuned to (Z)-9-hexadecenal and (Z)-9-tetradecenal, whereas the smaller-spiking neuron was far more sensitive to (Z)-11-hexadecen-1-ol and to (Z)-11-hexadecenyl acetate than to (Z)-9-tetradecenal. Accepted: 29 September 1997     

Parasite levels in blue-black grassquits correlate with male displays but not female mate preference

The handicap principle proposes that male sexual ornaments anddisplays provide honest indicators of quality. Female preferencefor high-quality males, however, may be driven not only by geneticbenefits but also by indirect benefits. We investigated theimpact of parasitism on morphological, ornamental, and behavioralcharacteristics of male and female blue-black grassquits (Volatiniajacarina) in captivity. First, we tested whether male displaysand morphology were influenced by parasitism. Second, we assessedif females were attentive to variation in male morphology anddisplays linked to parasitism. Third, we tested whether parasitismin females influenced health and mate preferences. We maintained2 groups of birds in captivity: nonmedicated birds developedhigh levels of coccidian parasitism, whereas medicated birdswere free of parasitism. Parasitized males developed, relativeto nonparasitized males, lower weight/tarsus indices and mass.They also showed relative deficiencies in their displays, withless persistence and lower rates. Despite the negative effectsof parasitism on males, females did not prefer nonparasitizedmales. This held for both parasitized and nonparasitized females.Our data suggest that coccidian parasitism has adverse effectson morphological condition and expression of displays. Theseeffects, however, appear not to be attended to by females; moreover,female mate preferences appear not to be impacted by the threatof parasitism. It thus seems that female mate preferences maynot depend only on sexual characters affected by parasitismin this species.